I do used to buy coins when the price is fell back ward and there is a serious dumb. The coins must have fell back world to said 30% and sell when it is in positive of 10%. I have never make a serious loses but make a reasonable profit. I have decided to follow this ageing principle of buying low and sell high.
Buying after 30% dump and booking profits with 10% seems a working strategy as we do see dead cat's jump is most commonly happening pattern with all types of dump. But the big question is how often you will be getting entry point with such a strange trading strategy. I am afraid you might get entry points monthly once of twice as 30% dumps are not happening everyday.
Still this might be categorized as a working strategy as the success ratio must be higher with this strategy. Rare opportunities must be ignored for this reasons.